On 10/06/16 18:02, Will Deacon wrote:
On Fri, Jun 10, 2016 at 04:19:44PM +0100, Suzuki K Poulose wrote:
From: Steve Capper <steve.cap...@linaro.org>
It can be useful for JIT software to be aware of MIDR_EL1 and
REVIDR_EL1 to ascertain the presence of any core errata that could
affect codegen.
This patch exposes these registers through sysfs:
/sys/devices/system/cpu/cpu$ID/identification/midr
/sys/devices/system/cpu/cpu$ID/identification/revidr
+
+#define CPUINFO_ATTR_RO(_name)
\
+ static ssize_t show_##_name (struct device *dev,
\
+ struct device_attribute *attr, char *buf)
\
+ {
\
+ struct cpuinfo_arm64 *info = &per_cpu(cpu_data, dev->id);
\
+ if (!cpu_present(dev->id)) \
+ return -ENODEV;
\
+
\
+ if (info->reg_midr) \
+ return sprintf(buf, "0x%016x\n", info->reg_##_name);
\
Should this be 0x%08x, as these are 32-bit registers?
Yes. Will change it. As per Mark's comments, I can change them to 64bit in a
separate
patch.
+
+static int __init cpuinfo_regs_init(void)
+{
+ int cpu, finalcpu, ret;
+ struct device *dev;
+
+ for_each_present_cpu(cpu) {
+ dev = get_cpu_device(cpu);
+
+ if (!dev) {
+ ret = -ENODEV;
+ break;
+ }
+
+ ret = sysfs_create_group(&dev->kobj, &cpuregs_attr_group);
+ if (ret)
+ break;
+ }
+
+ if (!ret)
+ return 0;
+ /*
+ * We were unable to put down sysfs groups for all the CPUs, revert
+ * all the groups we have placed down s.t. none are visible.
+ * Otherwise we could give a misleading picture of what's present.
+ */
+ finalcpu = cpu;
+ for_each_present_cpu(cpu) {
+ if (cpu == finalcpu)
+ break;
+ dev = get_cpu_device(cpu);
+ if (dev)
+ sysfs_remove_group(&dev->kobj, &cpuregs_attr_group);
+ }
Can CPUs be removed from underneath us using unregister_cpu? If so, I
Yes. Good point. Though this is done at early boot, nobody prevents
an unregister_cpu(). The safer way would be to wrap the code in
cpu_hotplug_disable()...enable().
I will respin it.
don't think we should assume that get_cpu_device will succeed in the
same places for both the loops.
Thanks
Suzuki
